The present invention relates to an improved process for reacting a perfluoroalkyl iodide with an olefinic compound.
The free radical chain addition of perfluoroalkyl iodides (R.sub.F I) to olefinic groups has long been known. Free-radical addition to allyl compounds initiated by azoic initiators is described for example in U.S. Pat. Nos. 3,083,224, 3,145,222 and 3,257,407. However the yields are low. Attempts to improve the process included the use of amines and amine salts and of copper ions (French Pat. No. 2,103,459), but this did not result in substantial improvements in yield. In U.S. Pat. No. 4,387,254 a 100% conversion of R.sub.F I to the adduct is achieved using a 5-molar excess of allyl alcohol, mercurous or mercuric iodide as catalyst and dimethylformamide as solvent, making the process unacceptable for environmental reasons.
In European Patent Application EP 0,483,166 the synthesis of certain R.sub.F I/allyl alcohol addition products in high yield is described. The reaction is carried out in the presence of water, basic compounds, metal oxides, silver compounds or epoxy compounds and using 1% by weight azo-bis-isobutyronitrile (AIBN) as initiator. The amount of water to use ranges from 0.1 to 5 times the amount of R.sub.F I, but is preferably not more than equal in weight. However when this process is used for the addition of R.sub.F I to larger unsaturated molecules and especially to alcohols and diols containing more than 1 allyl group, as for instance described in copending patent application Ser. No. 08/270,083 now U.S. Pat. No. 5,991,261 issued on Feb. 13, 1995, yields are too low and the reaction rates are too slow to be practical.
By elimination of HI from the R.sub.F I olefin-adducts by treatment with a base, R.sub.F -substituted alkylenes are formed which are useful, either by themselves or as intermediates, as oil-and water repellent finishes for a wide variety of substrates such as textiles, paper, leather, wood, masonry, glass or metal.